The field of the present invention is vibratory screen separators and the screen assemblies therefor.
Vibratory screen separators have long been known which include a base, a resiliently mounted housing, a vibratory drive and screen assemblies positioned on the housing. These screen assemblies are typically circular or rectangular and are positioned between an inlet manifold mounted to or above the housing and an outlet manifold from the housing. Material from the inlet manifold passing through the screen is accumulated by the outlet manifold for discharge. Material which is too large to pass through the screen is conveyed to the edge of the screen where it is discharged through a separate outlet.
The screen assemblies associated with such systems typically include tensioned screen cloth extending across and bonded to a rigid frame. Rectangular screen frames often include ribs extending between the sides of the screen frame. The screen cloth is often bonded to these ribs as well.
Screens are known which employ a top screening screen and a bottom coarse support screen. Systems known as self-cleaning screen kits or assemblies incorporate a supporting perforated plate or coarse mesh screen on the underside of the screen assembly. Sliders are positioned within the frame between the screen cloth and the perforated plate or coarse screen. When vibrated, the sliders are supported by the perforated plate or coarse screen but are thrown against the screening cloth to help reduce blinding. Systems have included ribs across the frame to form compartments within which the sliders are confined.
In all such systems, the screen cloth which performs the principal screening is subject to abrasion and vibratory loads. Ultimately such screens fail if not replaced timely. Failure is sufficiently random with such screens that any timely replacement would leave a very large margin before most screens would fail. Consequently, it is very uneconomical to replace screens timely enough to avoid all screen failures.
Screen failure can be detrimental to the screening process because oversized materials are able to pass through the properly sized screening cloth to the outlet manifold. Means for detecting this failure in a timely basis is also quite difficult and requires almost constant surveillance. Automatic sensing systems are yet to be commercially implemented.